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Blastomycosis in Indiana over 30 years

July 15 2015

Blastomycosis is not currently a reportable disease in many US states, including Indiana. Though many cases are mild, blastomycosis can lead to severe sequelae including  disseminated infection, especially in immunocompromised individuals. There is mounting evidence that the incidence of blastomycosis in endemic areas may be on the rise.

Led by Dr Chadi Hage, Dr Marwan Azar and colleagues describe characteristics of 114 patients seen with blastomycosis in 4 hospitals in the endemic Marion County over a 30 year period.  Their report provides insights into the difficulty in diagnosis and treatment of very ill patients requiring ICU admission and those with meningitis, as well as the more typical ambulant patients. Thirty patients (27%) were diabetic, but only 18 patients were  (16%) immunosuppressed. Most were male (60%) and typically in their 40’s.

As expected the lungs (90%) and skin 32 (28%) were most commonly involved. Surprisingly CNS involvement was found in 9 patients (8%), seen by imaging. Numerous other sites of dissemination were found, especially in bones. The presentation required intensive care in 25 (23%) patients.


Number of new blastomycosis cases over time in Central Indiana ( from: Azar et al 2015)
 

Confirmed diagnosis required multiple approaches including direct microscopy (cytology) in 13 of 49 (27%) on BAL or percutaneous aspirate of lung, fungal culture 82 of 95 (86%) (only 6 from sputum), Blastomyces antigen (which cross-reacts with histoplasma antigen) in 40 of 48 (83%) patients and Histoplasma antigen in 33 of 46 (72%). Blastomyces antibody was only detected in 12 of 47 cases (27%), whereas histopathology was positive in 64 of 75 cases (85%).

Treatment with Amphotericin B was given to 48 patients and  itraconazole to 81 (87%), with  reasonable outcomes: 78% resolved their disease, 12 died, 11 (10%) in intensive care. There were 17 patients who developed adult respiratory distress syndrome (ARDS) and 8 died. The mortality appeared to be lower in those who received corticosteroids (33%) than those who did not (55%). Markers for a worse outcome were diabetes, immunosuppression and multilobar disease on chest imaging. The results overall supported an increase in the incidence of blastomycosis.

The introduction of a highly-sensitive and commercially-available assay for the detection of Blastomyces dermatitidis antigen in 2004 20, could have influenced the increased incidence of blastomycosis in Marion County , which then encouraged further investigations by microbiology , cytopathology or histopathology- which also were the requirements for definition of a case. Article link  

   Blasomycosis skin lesions on a scar line